The catalytic degradation of RO16 dye under dark ambient conditions using La-Ni-Nb-O-based powders

Abstract

Dyes released from textile industries present a big threat to the environment, and remediation of wastewaters became one of the major scientific challenges. In recent years, there has been a great need for catalysts that would oxidize pollutants under dark ambient conditions without the use of external stimulants like light, temperature, or additional chemicals such as O3, H2O2. Efficient work of these catalysts would significantly reduce the energy consumption. Among other materials, perovskite-type oxides with general formula ABO3 emerged as possible catalysts for dye degradation in the dark conditions. Lanthanum nickelates with single (LaNiO3) and layered perovskite structure (La4Ni3O10, La3Ni2O7, La2NiO4) showed good catalytic properties, due to the existence of nickel in two oxidation states (Ni2+ and Ni3+) and the oxygen non-stoichiometry in these materials [1]. This study presents structural, microstructural and catalytic properties of the LaNi1-xNbxO3-based (xNb = 0.000, 0,005 and 0,010; La-Ni-Nb-O) powders prepared by mechanical activation method. The XRD (X-Ray Diffraction) analysis revealed the existence of a multiphase oxide system, including layered structures of nickelates Lan+1NinO3n+1 (n = 3, 2, 1, 0) and NiO phase in all La-Ni-Nb-O-based powders. Also, the HRTEM (High Resolution Transmission Electron Microscopy) analysis confirmed the presence of structural polytypes in these powders. The catalytic properties of La-Ni-Nb-O-based powders were investigated by degradation of the anionic azo dye, Reactive Orange 16 (RO16), under dark ambient conditions at different pH values (3, 6.5, 9.5 and 11) and temperature of 20 °C. The best catalytic efficiency in the degradation of RO16 dye showed the sample with x(Nb) = 0.010 in acidic solution, where the residual of RO16 dye was about 4.5 % after 330 minutes. The reusability test for this powder in degradation process of RO16 dye showed that the sample with x(Nb) = 0.010 retained its catalytic activity during three cycles. 1. W. Zhong et al., Appl. Catal. A, Gen., 549 (2018) 302.